There is a wide variation in the visual color shade values of the teeth. There is also commonly found a wide variation within the same individual of the different teeth in the mouth, due to a variety of natural factors. Often, in the same individual for example, the natural color shade of the upper and lower canines are more “yellow” than the upper and lower central and lateral incisors and it is common to find that the upper (maxillary) teeth are generally “whiter” than the lower (mandibular) teeth. It is often also common to find that the anterior teeth are in general “whiter” than the posterior teeth. Known dental whitening treatments that will be described below do not appear to take into account any of these significant variations in baseline (pre-treatment) color shades which are normally present in the same individual patient prior to treatment. This means that whatever whitening result that is obtained using the various whitening techniques currently in use cannot in general be customized to a given patient's needs based on the initial differing baseline color shades values of the teeth that the patient presented with prior to treatment. It is therefore extremely unlikely to obtain a completely uniform final whitening result utilizing the current systems in use.
There are numerous over-the-counter consumer “whitening” products such as toothpastes, whitening strips and mouthwashes. These will not be discussed further.
The standard professional dental treatment for whitening teeth is to provide the user either by way of the dental office some form of dental tray appliance (custom made from dental molds taken from each patient and made to fit to each patient) and mild concentrations of a whitening agent for self-application at home. These treatments are commonly referred to as the “home” whitening method.
The anatomical area posterior to the terminal teeth on the right and left sides of either the upper and lower jaws is referred to as the retro-molar pad. The dental tray appliance is typically fabricated to cover these terminal teeth and their terminal borders are the retro-molar pads. There is significant variability between patients as to the size of their teeth, and the shape of their dental arches. In regards to fabricating a tray to properly cover all the teeth contained within any given arch, the variable width and length of the dental arch must be considered.
The user is instructed to fill the full arch dental tray with the mild whitening chemical agent (gel) and place the tray on the teeth for up to several hours each day over the course of a minimum of one to two weeks. The custom dental trays cover all the teeth either in the upper or lower jaw. This means that the user can whiten both the front and back teeth with this treatment method using one tray for the upper teeth and one tray for the lower teeth. This teeth whitening technique is referred to as a “compression” technique, as the whitening agent is mainly contained during treatment within the closed confines of the tray and not left exposed to the atmosphere.
It has been demonstrated that the use of a compression technique with whitening agents potentiates whitening as this encourages oxygen ions release by the whitening agent (the primary means of whitening the teeth) to migrate towards the inside of the enamel structure of the teeth rather than to be released into the surrounding air (Miara and Miara, 2003).
It has been demonstrated that the natural saliva in the oral cavity contains a peroxidase enzyme which naturally breaks down and neutralizes hydrogen peroxide (Tenovuo and Pruitt, 1984). Utilizing custom made professional whitening trays which adapt to the teeth more closely than over the counter stock whitening trays reduces the amount of saliva that can seep into the trays and come in contact with the active hydrogen peroxide that has been placed into the trays. This reduces the amount of deactivation or breakdown by the saliva of the active gel and so increases the chemical whitening effect of this professional whitening treatment in comparison to over the counter “stock” whitening trays (which are not as well adapted to the teeth and so allow a significant amount of saliva to leak into these trays).
The custom “whitening” dental tray appliance(s) of the “home” treatment method mentioned above requires two dental visits. During the first office visit, dental impressions of the dental arches are taken in the dental office from which are fabricated custom-fitted rigid or semi-rigid thin plastic “whitening” tray(s). These trays outer limiting surfaces can either be closely contoured to the teeth or made significantly larger than the teeth. The above “home” treatment method requires the user to devote considerable time (as mentioned above) to achieve a moderate degree of teeth whitening, and due to the excessive exposure time of the teeth and gums to the whitening agents can often cause the teeth to become sensitive as well as irritating or chemically burning the gum and oral mucosal tissues of the mouth. Many patients find the effort required to achieve a sufficiently “whiter teeth” result too taxing, and there is often a very high rate of non-compliance, resulting in a poor final whitening result of the teeth.
These obvious drawbacks in the professional “home” whitening treatment method has in recent years given rise to professional dental treatments referred to in the dental field as “in office” or “power whitening” treatment. This treatment method involves applying in the dental office, utilizing and under the supervision of professional dental staff, more highly concentrated (and more caustic) formulations of various teeth whitening chemical agents than were previously used for the “home” whitening treatments. This “power” teeth whitening technique typically takes around one hour treatment time. To protect the gingival tissues from these highly concentrated whitening agents, a “paint-on dam” or protective coating (a layer of material applied in a strip at the gum line which is placed in a scalloped shape to contour to the gum-line) is applied by hand (very time-consuming) and hardened with a standard dental UV light. Additionally, an uncomfortable lip and cheek retractor device is inserted into the mouth along with cotton rolls (and gauze as needed) in order to try and protect the rest of the oral tissues of the mouth from these highly concentrated and caustic whitening agents.
These precautions are necessary, as contact of these highly concentrated chemical whitening agents used in the “power” whitening with the above mentioned soft tissues of the mouth will, in a few seconds, cause significant chemical burning and pain to the patient. Typically, three applications of the whitening agent (for approximately 20 minutes each) limited to only the buccal (front) surfaces of only the anterior teeth are made, wherein the previous application is washed and suctioned off the teeth and replaced with the next application. The lingual (inner) surfaces of these anterior teeth and the posterior teeth in their entirety are not “whitened” using this technique. The “power” whitening technique does not utilize a tray device of any kind. The whitening agent is applied in an open “non-compressed” paint-on manner onto the external buccal surfaces of the limited teeth to be treated and so does not have the whitening advantages of the compression effect of the whitening gel using trays as described previously (home whitening technique).
Over the past two decades there has also been a shift in “in office” or “power whitening” treatments to utilize “light activated” whitening agents over the older whitening agents that did not require light activation to potentiate an oxidation (whitening) chemical reaction. These newer light activated whitening agents are chemically formulated to oxidize when exposed to a concentrated intense light source which acts as a catalyst to potentiate the chemical oxidation of these whitening agents.
There is much controversy in the dental field as to whether the use of light activation of the whitening gels enhances the chemical whitening effect of these gels. It has been postulated that it is actually the heat generated by the light and not any specific wavelength of the light that actually increases the chemical activity and hence the whitening activity of these whitening gels.
The light emitting devices currently being used in the dental field can, in general, only reach the anterior portion of the mouth and only after the lips and cheeks have been retracted using devices as were described above. This is due to the limited natural elasticity of the lips and muscles surrounding the mouth which limit the number of teeth that can comfortably and safely retracted and exposed to the light source and the highly concentrated “power” whitening chemical agents while still protecting the soft tissues of the oral cavity from these highly caustic whitening agents.
As mentioned above, these limitations typically result in “power whitening” treatments of, at a maximum, the front upper 10 and front lower 10 teeth, (the upper and lower central and lateral incisors, canines and first and second bicuspids) for a maximum treatment of 20 teeth (there are typically 28-32 teeth in the human mouth). Due to the limitations already mentioned, it is common practice to find that only the top 8 and bottom 8 front teeth are “power” whitened for a total of 16 (only 50%) of the teeth often present in the patient's mouth, a distinct disadvantage of this teeth whitening technique.
A further limitation of the treatment area is that in general the lights used in the “power” whitening can be positioned by the operator into the patient's mouth to illuminate mainly the buccal (front or outer) surfaces of the anterior teeth while only poorly illuminating the lingual (back or inner) surfaces of these front teeth. It is also extremely difficult for the dental practitioner to apply the “paint-on dam” protective coating at the gum-line of the lingual “inner” surfaces of the anterior teeth and almost impossible for the dentist to isolate the very active tongue with the current isolation devices and materials available in the dental field. This means that these sensitive oral tissues are extremely difficult to isolate from the caustic chemical burning of the highly concentrated “power” whitening agents.
The above explains why whitening of the inner (lingual) surfaces of the anterior teeth are rarely done in this technique and the posterior teeth are never whitened at all with this technique. Moreover, the “power” whitening of only the buccal (outer) surfaces of the anterior teeth adversely affects the overall final whitening result, as the natural enamel layers of the teeth (naturally found on both outer and inner surfaces of all the teeth) are naturally somewhat translucent. This allows for the “darker” shade of the inner (lingual) untreated surfaces of the teeth to “show through” to the front surfaces. This naturally occurring optical effect can “bring down” or diminish the overall final whitening effect of these teeth when using the current “power” whitening treatment method.
Advantages of the “in office” or “power” whitening treatment method compared to the “home” treatment include: a. It allows for the more rapid whitening of the teeth compared to the “home” treatment due to the use of more highly concentrated whitening agents. This reduces significantly the over-all treatment time; b. As it is done “in-office”, there is less of a non-compliance issue with the patient as is often encountered with the more lengthy “home” treatment; and c. The shorter treatment time tends to minimize the irritation or sensitivity of the teeth, as the teeth are exposed to these agents for a shorter period of time, though some users do experience teeth sensitivity due to the more concentrated strength of the chemical oxidizing agents used in this treatment method and the often encountered unwanted leakage of small amounts of the highly concentrated whitening agents past the protective barriers placed by the dental practitioner onto the oral tissues during the “power” whitening treatment.
Disadvantages of the “in office” treatment method compared to the “home” treatment include: a. As noted above, only the front teeth can be comfortably whitened with the “in office” method, as compared to the “home” treatment which allows for the whitening of both the front and back teeth; b. As mentioned above, the more highly concentrated formulations of the whitening oxidizing agents are more caustic to the hard (tooth) tissue and soft (gums, oral mucosa, tongue) tissue of the mouth and so require the application of special hand-applied gingival and oral mucosal barriers by professional dental staff under the supervision of a dentist or by the dentist him/herself on the gingival and oral mucosal tissues of the areas to be treated in order to protect them from these highly concentrated whitening chemicals. This is a time-consuming procedure that often needs to be reapplied during treatment to properly protect the soft tissues of the mouth form these highly concentrated whitening agents. Even with all this isolation effort, as mentioned above, it is typical to find some leakage and burning of the oral tissues of the patient resulting in temporary pain and discomfort to the patient; c. Due to the inaccessibility of the posterior teeth and difficulty (due to the cheeks and tongue) of the posterior areas of the mouth, these whitening treatments invariably are restricted or limited (due to the extreme difficulty of protecting the oral soft tissues surrounding the posterior teeth) to the anterior segments of the mouth; d. Whitens mainly the front (buccal) surfaces of the anterior teeth and only rarely is used to whiten the inner (lingual) surfaces of the anterior teeth; and e. It is common to observe a more marked “rebound” effect (loss of whitening result) after treatment with this “in office” treatment method as compared to the “home” treatment method. This is due to the short duration of treatment (as compared to the much longer treatment time of the “home” treatment method) and the resultant rehydration of the teeth after treatment (the “power” whitening process tends to temporarily dehydrate the teeth which temporarily potentiates the initial whitening result). This means that the typical final “whitening” result using the “power” whitening technique is significantly poorer then the final “whitening” result that can be obtained when the patient is highly compliant and uses the “home” whitening technique properly.